Before you start

An unlocked phone (a carrier-locked phone from home may not accept a Colombian SIM)
Your passport (required by law to register any prepaid SIM in your name)
Your phone's IMEI number, found by dialing *#06# (needed for device registration)
Proof of purchase / receipt for a phone bought abroad, in case the carrier asks for it during IMEI registration

Step-by-step

1
Land connected with an eSIM (before you fly)
If your phone supports eSIM, install an Airalo or Holafly Colombia plan before departure so you have data the moment you land at José María Córdova (MDE) airport. Airalo starts around US$4.50 for 1 GB / 7 days and scales up to multi-GB monthly bundles; Holafly sells unlimited-data plans from roughly US$19-54 for 5-20 days. The plan only starts counting once you connect on arrival, so you can install it days ahead.
Mobile appWho: You, via the Airalo or Holafly app5-10 minutes to install; activates on arrivalUS$4.50-54 (COP ~19,000-235,000) depending on data and days
2
Buy a prepaid (prepago) SIM with your passport
Go to an official Claro, Movistar, Tigo, or WOM store (city-centre branches and malls like El Tesoro or Santafé are cheaper than the airport, which marks up 20-50%). Show your passport; the clerk registers the SIM in your name as Colombian law requires and sets it up on the spot. The SIM itself is free to about COP 6,000 (under US$1.50); Tigo SIMs are often free, Claro around COP 3,000-5,000. Choose Claro for the best coverage or WOM to save money in the city.
In personWho: You, at a carrier store or authorized dealer15-30 minutes in storeCOP 0-6,000 (US$0-1.50) for the SIM
3
Register your phone's IMEI so it isn't blocked
This is the critical step foreigners miss. Colombia's anti-theft system blocks any unregistered foreign device after roughly 20-30 days (you'll start getting warning SMS first). The easiest path is to ask the store clerk to register your IMEI when you buy the SIM: they need your passport and the IMEI (dial *#06#), and may ask for the phone's receipt to prove it isn't stolen. Claro customers can also register in-app or via *611#. Do this immediately, not when the warnings start.
In personWho: Carrier store staff (or yourself in the carrier app)5 minutes; activation can take up to ~2 business daysFree
4
Top up (recargas) and add a data plan with WhatsApp
Prepaid runs on recargas (top-ups). Buy a data bundle in the carrier app or top up at any corner shop, pharmacy, or supermarket (Éxito, Justo y Bueno) showing a 'recarga' sign, or in OXXO/convenience stores. Typical bundles run COP 16,000-41,000 (US$ ~4-10) for 9-32 GB over 15-30 days with unlimited calls and texts, and most include free WhatsApp and Facebook. Dial *611# (Claro) to check balance and see your number.
Mobile appWho: You, via the carrier app or any recarga point2-5 minutes, anytimeCOP 16,000-41,000 (US$ ~4-10) per monthly data bundle
5
Set up home internet if you're staying (optional)
For a longer stay, Claro, Tigo (Tigo-UNE, which absorbed EPM's old UNE network), and Movistar offer fibre/FTTH home internet across Medellín; smaller players like Somos Internet compete in some buildings. Plans run roughly COP 70,000-170,000/month (US$ ~16-40) for 200-700 Mbps, often symmetrical. Many furnished apartments already include WiFi, so check before signing a contract, which usually needs a cédula or a guarantor.
In personWho: You (cédula or local guarantor usually required for a contract)A few days to schedule installationCOP 70,000-170,000/month (US$ ~16-40)

Documents you’ll need

Passport (mandatory to register any prepaid SIM)
Phone IMEI number (dial *#06#)
Proof of purchase / receipt for a foreign-bought phone (for IMEI registration)
Cédula de extranjería (only for postpaid pospago contracts or home-internet plans)

Things most newcomers don’t know

Register your phone's IMEI right away, even though nothing forces you to at purchase. A foreign device that isn't registered in Colombia's anti-theft database gets cut off the network after roughly 20-30 days, and the warning SMS are easy to ignore until your phone suddenly stops working.

Colombia runs a strict positive/negative IMEI database (BDA) to fight rampant phone theft; the carrier links your registered SIM to a legal, recognized device. This trips up foreigners constantly because buying the SIM feels complete, but device registration is a separate step.

Source: MinTIC / CRC IMEI verification rules and Medellín Guru

Pick your carrier by coverage-vs-price: Claro is the most expensive but has the widest, most reliable network and the most 5G; WOM is the cheapest with solid data in central Medellín but spottier coverage and no 5G yet.

Claro holds the largest share of mobile sites and most of Colombia's 5G sites, so it just works almost everywhere; WOM is the newer budget entrant optimizing for cities. In Medellín itself all four are fine, so the choice is really price vs travel-outside-the-city reliability.

Source: CRC/Opensignal coverage reports and Traveltomtom 2025

A prepaid SIM is one of the lowest-friction things you'll do in Colombia: passport, a few minutes, and under US$2 for the SIM, no local bank account or cédula needed.

Unlike postpaid (pospago), which requires a cédula and credit history, prepago is built for walk-in customers. The only legal requirement is registering the SIM to your passport, which the clerk handles, so newcomers can be connected on day one.

Source: Traveltomtom and Phone Travel Wiz 2025 SIM guides

WhatsApp is the operating system of Colombian life, so getting a working number connected to it matters more than raw data: businesses, landlords, doctors, and taxis all run on WhatsApp, and most prepaid plans bundle it free.

Phone calls and email are secondary here; people expect to reach you on WhatsApp. Buying an eSIM before you fly means you land with a number already active on WhatsApp instead of being unreachable until you find a store.

Source: Tom Plan My Trip and Airalo/Holafly eSIM guides

Common mistakes to avoid

Not registering your foreign phone's IMEI and getting silently cut off the network after 20-30 days, then scrambling to reconnect.
Buying your SIM at Medellín airport (MDE) where the same plan costs 20-50% more than a city-centre or mall store a day later.
Bringing a phone that's carrier-locked from your home country, so it rejects the Colombian SIM entirely; confirm it's unlocked before you travel.
Choosing WOM purely on price and then losing signal the moment you leave the city for a weekend trip, since its coverage is thinner than Claro's.